EP0139638B1 - Isolierungsanalysierungsvorrichtung und verfahren - Google Patents

Isolierungsanalysierungsvorrichtung und verfahren Download PDF

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Publication number
EP0139638B1
EP0139638B1 EP83901473A EP83901473A EP0139638B1 EP 0139638 B1 EP0139638 B1 EP 0139638B1 EP 83901473 A EP83901473 A EP 83901473A EP 83901473 A EP83901473 A EP 83901473A EP 0139638 B1 EP0139638 B1 EP 0139638B1
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European Patent Office
Prior art keywords
signal
insulation
current
time
constant
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EP83901473A
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English (en)
French (fr)
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EP0139638A1 (de
EP0139638A4 (de
Inventor
Steven A. Leszczynski
Peter H. Reynolds
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults

Definitions

  • the present invention relates to measurement of insulation resistance, and other related properties of a specimen.
  • the apparatus and method claimed (claims 1 and 3) is a refinement and improvement of apparatus and method disclosed in U.S. Patent Cooperation Treaty patent application Serial No. 81/01647, filed December 14,1981, the invention of Peter H. Reynolds. Using such improvements, it is able to achieve high accuracy over a wider range of measured parameters (see also Internationale Electronische Rundschau, Vol. 26, No 8, August 1972, pages 184 ⁇ 188; F. Wolf:" Digital and analog an accordendes Tera-Ohmmeter mit Kontinuierlich ein combiner Mesnaps").
  • E. B Curdts described a method of calculating i c from I TOT .
  • the derived equation is where i 1 , i 3 . 16 and i 10 are three different values of I TOT measured at different times, based on a constant unit of time multiplied by their subscripts, i.e., 1, 3.16 and 10 minutes.
  • the equation assumed that the unit time chosen was long enough such that ig, the geometric capacitance charging current, has become negligible. In application of this equation, however, some limitations may be encountered to which the following two case examples are illustrative.
  • the total current in a capacitive sample is made up of three components such that as represented in the schematic circuit diagram of Fig. 1.
  • Fig. 1 has been discussed above and in the parent United States Patent Cooperation Treaty application.
  • the microprocessor 13 is the central element of the instrument. Its functions include sequencing of the test, switching signal paths, controlling the elapsed timer clock, gathering data, performing all necessary mathematical manipulations, making decisions relative to the data obtained, converting the data gathered to readable English format and controlling both an output device (printer) and input device (keyboard).
  • the memory 15 serves to store the list of actions and sequence of operations necessary to perform the test. Collectively this set of instructions is referred to herein as the instrument program.
  • Another section of memory 15 acts as a storage area where the microprocessor 13 stores data during the test sequence for future use.
  • the basic test circuit is comprised of d.c. supply 1, a sense resistor (Rs) 2, and the Specimen 5 under test connected to the instrument via connections 4 and 6.
  • the d.c. supply 1 is programmed by the microprocessor to the desired test voltage.
  • the d.c. supply can also be switched in or out of the test circuit by the microprocessor.
  • I TOT ' a voltage sense and level shift amplifier 3 is attached across the sense resistor.
  • This amplifier has a high impedance input so that the effect of loading upon the sense resistor 2 is negligable with regard to circuit operation.
  • the voltage sensor portion of device 3 measures this voltage and amplifies it with a gain which is set by the microprocessor 13 to provide the widest dynamic range and best resolution possible for the specimen being tested. Since neither side of the sense resistor 2 is at ground potential, the resultant amplified signal generated by the voltage sense portion of 3 is also not ground referenced. In fact, the signal may be at a potential of several thousands volts removed from ground.
  • a level shift is incorporated to move the differentially generated I TOT signal to a ground referenced I ToT which is the second function of the voltage sense and level shift amplifier 3.
  • the algorithm based on the foregoing mathematical analysis and employed in the embodiment requires that the solution to the equations is based upon the value of I TOT ' (the derivative of I TOT ). For this reason the signal path exiting amplifier 3 is split in two.
  • One path of the I TOT signal is fed into an analog to digital converter (A/D) 7 which is under microprocessor 13 control and can convert the magnitude of I TOT to a digital form (numerical value) for use within the microprocessor.
  • the other path of the I ToT signal is fed to a differentiator (d/dt) 8 which produces the desired differentiated signal I TOT '.
  • the gain of the differentiator 8 described in the algorithm as the quantity K is controlled by the microprocessor 13 to ensure that the differentiator 8 has ample dynamic range and resolution'to ensure high accuracy results.
  • the I ToT ' signal path feeds both the sample/hold memory 9 and one side of the comparator 11.
  • the algorithm describes the need to measure the elapsed time it takes the I ToT ' signal magnitude to drop in magnitude by half.
  • the sample/hold memory 9 is used to store, by analog means, the initial value of I TOT '.
  • the state of the sample/hold memory 9 is controlled by the microprocessor 13. When in the sample mode, the output of the sample/hold memory simply follows or tracks the input magnitude.
  • the output value is held constant so that it no longer tracks the input signal. This is accomplished by trapping voltage on a capacitor by using a very high impedance buffer and a switch.
  • the output of the sample/hold memory 9 retains or stores the magnitude of what the I TOT ' signal was at the instant in time when the sample/hold memory 9 was instructed to hold.
  • the precision voltage divider 10 establishes an output of 0.5 times the input value and places this signal into the second side of comparator 11 for comparison with the instanteous value of I TOT ' (stored).
  • the time it takes for the ' TOT ' signal to drop in magnitude by 50% as described in the algorithm is measured by an elapsed time counter 12.
  • the microprocessor 13 gathers such elapsed time data from the elapsed time counter 12 via signal path 16.
  • the microprocessor 13, and the associated memory 15 are programmed to compute and from this This value may then be displayed on the display of display and controls 14, either as an analog or digital display or directly printed by a printer or any other convenient method of indicating the result.
  • Display and controls 14 also incorporates controls to permit the operator to control the ranges and other settings of the apparatus. Since the value of i c and E s are both known, the microprocessor 13 can be programmed to calculate the true insulation resistance value. This value can be displayed on display 14 in place of or in addition to the value of i c .
  • the apparatus can measure and store values of I ToT , it is also possible to measure the value of apparent insulation resistance, which is the "insulation resistance” measured by conventional megohmmeters such as the "Megger"° range of insulation testers made by the James G. Biddle Co. of Blue Bell, PA.
  • insulation resistance measured by conventional megohmmeters such as the "Megger"° range of insulation testers made by the James G. Biddle Co. of Blue Bell, PA.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Resistance Or Impedance (AREA)
  • Formation Of Insulating Films (AREA)

Claims (3)

1. Gerät zur Berechnung des Kriechstromes ic als ein Mass des Isolationswiderstandes für eine Isolationsprobe (5) mit:
Mitteln (3) zum Ablesen von Spannung an einer Leseimpedanz (2) in einer Schaltung mit einer Spannungsversorgung (1) und einer Isolationsprobe (5) zum Erzeugen eines den Isolationsgesamtstrom ITOT darstellenden Signals,
Mitteln (7) zum Umwandeln des Isolationsstromgesamtsignals in digitale Form,
den Isolationsgesamtstrom zeitlich differenzierende Mittel (3) zum Erzeugen eines ersten abgeleiteten Signals,
Abtastmittel (9, 10) zum Auswählen und Halten eines festen Momentanwertes des besagten ersten abgeleiteten Signals und zum Erhalten eines vorbestimmten Anteiles R des besagten ersten festen abgeleiteten Signals, -
Vergleichermittel (11) zum Aufnehmen und Vergleichen besagten vorbestimmten Anteiles R des besagten ersten festen Ableitungssignals mit dem ersten abgeleiteten Signal,
einem Zeitablaufrechner (12), der von dem Vergleicher (11) ein Ausgangssignal erhält, womit von der Zeit Z der Probennahme bis zur Zeit, zu der die verglichenen Signale einander gleich sind, eine Messung durchgeführt werden kann,
Mittel (13) zum Aufnehmen der Zeitablaufinformation zum Berechnen einer Konstante n entsprechend der folgenden Formel
Figure imgb0023
und zum Anlegen der Konstante an die digitale Darstellung des Isolationsgesamtstromes und zur Berechnung des Kriechstromes unter Verwendung der folgenden Formel
Figure imgb0024
wobei X und Y vorbestimmte Zeiten sind.
2. Gerät nach Anspruch 1, dadurch gekennzeichnet, dass mindestens die Mittel (13) zur Berechnung der Konstanten n und zur Berechnung des Kriechstromes durch einen Mikroprozessor bereitgestellt werden.
3. Verfahren zur Berechnung des Kriechstromes ic als einem Mass des Isolationswiderstandes in einer Isolationsprobe mit:
Lesen der Stromhöhe in der Isolationsprobe mit Analyse zur Erzeugung eines den Isolationsgesamtstrom ITOT darstellenden Signals,
Umwandeln dieses Isolationsgesamtstromsignals in Digitalform und Einspeisen desselben in Rechnermittel,
zeitlichem Differenzieren des Isolationsgesamtstromsignals,
Abtasten eines Festteils des differenzierten Signals zu einer Zeit, zu der ein konstantes Signal mit Festwert sicher erhalten werden kann,
Entnahme eines vorbestimmten Anteils R des abgetasteten konstanten Signals mit Festwert,
Vergleichen des vorbestimmten Anteiles des konstanten Festwertes mit dem differenzierten Signal über eine Zeitperiode,
Messen der abgelaufenen Zeit Z, die von dem Differenzialsignal dafür benötigt wird, denselben Wert wie der vorbestimmte Anteil des konstanten Signals mit Festwert zu erreichen,
Berechnen einer Gleichungskonstanten n aus der besagten abgelaufenen Zeit nach der Formel:
Figure imgb0025
und
Berechnen des Kriechstromes (ic) in der Isolationsprobe mit Verwendung des abgeleiteten n in der folgenden Formel:
Figure imgb0026
wobei X und Y vorbestimmte Zeiten sind.
EP83901473A 1983-03-14 1983-03-14 Isolierungsanalysierungsvorrichtung und verfahren Expired EP0139638B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT83901473T ATE40218T1 (de) 1983-03-14 1983-03-14 Isolierungsanalysierungsvorrichtung und verfahren.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1983/000374 WO1984003772A1 (en) 1983-03-14 1983-03-14 Insulation analyzer and method

Publications (3)

Publication Number Publication Date
EP0139638A1 EP0139638A1 (de) 1985-05-08
EP0139638A4 EP0139638A4 (de) 1986-02-10
EP0139638B1 true EP0139638B1 (de) 1989-01-18

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Family Applications (1)

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EP83901473A Expired EP0139638B1 (de) 1983-03-14 1983-03-14 Isolierungsanalysierungsvorrichtung und verfahren

Country Status (5)

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EP (1) EP0139638B1 (de)
JP (1) JPS60500881A (de)
AT (1) ATE40218T1 (de)
DE (1) DE3378996D1 (de)
WO (1) WO1984003772A1 (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NZ217223A (en) * 1986-08-15 1990-04-26 Fisher & Paykel Measuring sensor resistance as a function of rc charge/ discharge time
FR2634899B1 (fr) * 1988-07-28 1990-11-30 Merlin Gerin Circuit d'entree, du type tout ou rien, d'un automate programmable

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2916697A (en) * 1955-07-05 1959-12-08 Bourns Inc Insulation resistance measuring circuit
US3437925A (en) * 1965-10-23 1969-04-08 Dana Lab Inc Circuit for converting resistance values of unknown resistor to electrical potential signal for measurement purposes
US4217543A (en) * 1977-05-23 1980-08-12 John Fluke Mfg. Co., Inc. Digital conductance meter

Also Published As

Publication number Publication date
EP0139638A1 (de) 1985-05-08
DE3378996D1 (en) 1989-02-23
JPS60500881A (ja) 1985-06-06
JPH0546505B2 (de) 1993-07-14
WO1984003772A1 (en) 1984-09-27
EP0139638A4 (de) 1986-02-10
ATE40218T1 (de) 1989-02-15

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